The NSO will not display the E key after approaching the building vehicle terminal, but into the module block. In order to use the vehicle's terminal, you need to run to a farther position on the side.
If the vehicle terminal can't be accessed due to low Cortium (it gets locked for anyone not in the builder's squad at less than 20k), then the module slots take priority over the "restricted" message, when standing on the stairs. If you stand on the vehicle pad it self, then it will prioritize the terminal and tell you that it is, in fact, "restricted". I have never had the priority bug when there was enough Cortium.
This behavior also happens if the terminal is accessible. Cortium levels don't really effect it. I usually just end up filling the module slots so I can use the terminal without having to risk being roadkilled by my own vehicle pull.
I have been reporting this bug in game since the new Construction update. It's not just NSO, I have experienced it on NC and TR as well. All my in game bug reports amounted to nothing though - for such a vital element of the game - the pulling of vehicles on Oshur for instance, it is alarming nothing gets done. I have died countless times as a Light Vehicle Terminal trying to find the E message to pull a vehicle to defend a player base. It seems to me the E button message is not on the front of the terminal its floating around somewhere at the back of the terminal. The times I have pulled a vehicle by finding the E button at the back of the terminal there is a very good chance I get mowed down by my own vehicle. This has happened at bases with a full cortium silo so maybe the cortium went to low to pull a vehicle, but then when the silo was filled up it didn't switch back to give you vehicle access. But that doesn't explain the fact, you can't find the E button which is floating around in the ether. It only happens at the Light Vehicle Terminal and not the Vehicle Terminal in the Command Centre. The Command Centre terminal is slightly off as well; if you face the terminal it is simply not there; you have to be at a 45 degree angel to find the E button message.